Summary

Description

A buff-coloured snail that grows up to 5 mm high. The animal has a cylindrical snout ending in a rounded mouth disc. It has a peculiar looping gait.

Recorded distribution in Britain and Ireland

Recorded from Pagham Harbour, West Sussex; The Solent, Isle of Wight, The Fleet, Dorset and St Mawes Bay, Cornwall.

Global distribution

From the Channel coasts of France and Britain to the Mediterranean, the Black Sea, and on the Canaries, Madeira and Azores.

Habitat

Found in shingle amongst rotting vegetation and fine sediment at a depth of 15 cm, at high water mark and more rarely in muddy habitats under stones at the high water mark. It is often associated with the plants Suaeda maritima, Suaeda vera and Atriplex (Halimione) portulacoides.

Depth range

-

Identifying features

The juvenile has a typical spire-shaped shell; later whorls are parallel-sided until maturity when the tapered part is broken off, leaving a suture line. The adult shell is thus truncated and more or less cylindrical.

Buff-coloured, 5 mm high.

Animal with cylindrical snout ending in a rounded mouth disc.

Additional information

Abscission of the earlier part of the shell is presumably an adaptation to an interstial habitat.
The taxonomy of the Gastropoda has been recently revised (see Ponder & Lindberg 1997, and Taylor 1996). Ponder & Lindberg (1997) suggest that Mesogastropoda should be included in a monophyletic clade, the Caenogastropoda.

Habitat Information

Formerly known from 12 sites in Britain, from Porthcurno along the south coast to the rivers Orwell and Deben, Suffolk. Presently known to be living in only five locations. It is a southern species which reaches its most northerly distribution in Britain. Paludinella globularis (as littorina), Ovatella myosotis and Leucophytia bidentata are associates.

Larval characteristics

Larval/propagule type

-

Larval/juvenile development

Oviparous

Duration of larval stage

Not relevant

Larval dispersal potential

<10 m

Larval settlement period

Insufficient information

Life history information

Egg capsules are laid of 0.75-0.80mm diameter, which are spherical and surrounded by a thick wall. Each capsule contains one egg and they are attached singly to pieces of detritus in the habitat in which the adults live. Small snails are hatched with a shell of 0.65mm (Fretter & Graham, 1978)

This MarLIN sensitivity assessment has been superseded by the MarESA approach to sensitivity assessment. MarLIN assessments used an approach that has now been modified to reflect the most recent conservation imperatives and terminology and are due to be updated by 2016/17.

Physical pressures

The species would be removed with substratum loss and may be damaged during the process. It has low recoverability as it lacks an aquatic dispersal phase and living populations are only known from three locations in the UK.

Smothering could block shingle interstices and prevent movement of the snail and reduce the level of oxygenation. Recovery would be low because it lacks an aquatic dispersal phase and living populations are only known from five locations in the UK.

Truncatella subcylindrica lives in estuaries and lagoons amongst fine muddy sediment so would be able to tolerate increased siltation. Indeed, some increased siltation may be beneficial to feeding as it is a deposit feeder, so long as interstices remain clear.

The mollusc is adapted to avoid desiccation by having a hard shell and operculum. Where it is interstitial, the species would also be protected from desiccation by the depth of sediment above it and where the species is epifaunal would avoid desiccation by hiding in crevices or under stones.

Living at high water mark, the species is inundated for only short periods, so that increased water flow is unlikely to have a significant effect unless it is so great as to erode materials and animals.

The degree of temperature tolerance of Truncatella subcylindrica is not known. The species will be sheltered from temperature extremes to some extent by its hard shell and by its interstitial habitat. However, the species may be intolerant of decreases in temperature as it is at the northern limit of its distribution.

The high water mark habitat means that the species is only subject to wave action for short periods. However, increased wave action may damage or wash it away, or move shingle damaging the animal by abrasion.

Additional information

Importance review

Policy/legislation

Status

Non-native

Native

-

Origin

-

Date Arrived

-

Native

-

Origin

-

Date Arrived

-

Importance information

The assemblage is of low diversity and biomass occupying only a small proportion of the space available. It is unlikely to provide a unique food source, although a nemertean predator Prosorhochmus claparedii is recorded from the same niche at the Fleet (R.S.K. Barnes, per. comm.)

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